I basically see two reasons for a going public: Glencore gets access to more money. It is a way of funding your business and to finance growth. Plus: You have more liquid shares. It is easier to leave the company and redeem your shares. The 'going public' may also be an exit strategy for the top management.
I've had moments of thinking maybe I should go on Twitter. It's something that I've been shy about, and I've thought that maybe I should do it.